1. Field of the Invention
This invention relates to metallocene compounds, processes for the production of olefin polymers using olefin polymerization catalysts containing the metallocene compounds, and the olefin polymers obtained by the production processes.
2. Related Background Art
In the past there have been reported processes for the production of propylene polymers by using catalysts that contain various metallocene compounds having specifically substituted indenyl ligands (for example, JP-A-06-184179, JP-A-06-100579, JP-A-07-188318, WO 01/48034, JP-A-10-87716, JP-A-08-67689 and WO 97/40075).
Such catalysts containing metallocene compounds are, however, generally costly. For this reason, in order to reduce the production costs of the propylene polymers obtained using such catalysts, further improvement in the polymerizing activity of the catalysts has been desired.
These metallocene compounds have been typically developed with the aim to enabling high molecular weight propylene polymers to be produced as well as to enabling the stereoregularity of the produced propylene polymers to be highly controlled; however, they have not yet come to meeting the desired performance sufficiently.
In addition, it is reported that when a catalyst containing a metallocene compound is used to produce a propylene/ethylene copolymer, the molecular weight of the produced copolymer typically decreases greatly as the content of ethylene unit increases (e.g., T. Sugano, “SPO '99(1999)”, pp. 31–53). For this reason, the development of catalysts has been desired such that they contain metallocene compounds and can produce propylene/ethylene copolymers with sufficiently high molecular weight even if their contents of ethylene units are high.
There are also reported the instances where catalysts containing metallocene compounds are used to produce propylene/1-butene copolymers (e.g., see JP-A-08-208909 and JP-A-08-283343). Nevertheless, the development of catalysts has been desired such that they can produce propylene/1-butene copolymers with sufficiently high molecular weight only at practically high polymerization temperatures without causing polymerization at low temperatures.